Dates and times
| Year | March equinox | June solstice | September equinox | December solstice |
|---|---|---|---|---|
| 2025 | 20 Mar, 09:01 | 21 Jun, 02:42 | 22 Sep, 18:19 | 21 Dec, 15:02 |
| 2026 | 20 Mar, 14:45 | 21 Jun, 08:24 | 23 Sep, 00:05 | 21 Dec, 20:50 |
| 2027 | 20 Mar, 20:24 | 21 Jun, 14:10 | 23 Sep, 06:01 | 22 Dec, 02:42 |
| 2028 | 20 Mar, 02:16 | 20 Jun, 20:01 | 22 Sep, 11:45 | 21 Dec, 08:19 |
| 2029 | 20 Mar, 08:01 | 21 Jun, 01:48 | 22 Sep, 17:38 | 21 Dec, 14:13 |
| 2030 | 20 Mar, 13:51 | 21 Jun, 07:31 | 22 Sep, 23:26 | 21 Dec, 20:09 |
| 2031 | 20 Mar, 19:40 | 21 Jun, 13:16 | 23 Sep, 05:15 | 22 Dec, 01:55 |
| 2032 | 20 Mar, 01:21 | 20 Jun, 19:08 | 22 Sep, 11:10 | 21 Dec, 07:55 |
| 2033 | 20 Mar, 07:22 | 21 Jun, 01:00 | 22 Sep, 16:51 | 21 Dec, 13:45 |
| 2034 | 20 Mar, 13:17 | 21 Jun, 06:43 | 22 Sep, 22:39 | 21 Dec, 19:33 |
Times are in UTC. Add your offset — a December solstice at 15:50 UTC is 16:50 in Berlin and 10:50 in New York — which is why the calendar date can differ between continents.
What happens at each one
An equinox is the instant the sun crosses the celestial equator — its declination passes through zero. A solstice is the instant it is furthest north (June) or south (December), at ±23.44°. Astronomers define them by the sun's apparent ecliptic longitude: 0°, 90°, 180° and 270°. The table was computed exactly that way with the NREL Solar Position Algorithm.
| Latitude | Day length, June solstice | Day length, December solstice |
|---|---|---|
| 0° (equator) | 12 h 07 min | 12 h 07 min |
| 30° N | about 14 h 05 min | about 10 h 13 min |
| 40° N | about 15 h 00 min | about 9 h 20 min |
| 50° N | about 16 h 22 min | about 8 h 05 min |
| 60° N | about 18 h 50 min | about 5 h 50 min |
Days are slightly longer than twelve hours even at the equinox because sunrise and sunset are counted from the moment the sun's upper edge touches the horizon, and refraction lifts it by half a degree.
Why the dates move
The solar year lasts about 365.2422 days. Each calendar year the instants move about six hours later, then jump back when a leap day is added. That is why the June solstice falls on 20 or 21 June and the December solstice on 21 or 22 December.
What it means for solar panels
The December solstice is the design day for off-grid systems in the northern hemisphere: the lowest noon sun and the shortest day. It is also the day used to space rows of panels — see the row spacing calculator. The month around it is usually the darkest — though cloud can move the worst month to November or January.